LeafLabs Garden

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1. 

   MediumKahuna
   Member

   New to Leaf and just got some Maple RET6s
   Just wanted to report my (pleasant) experience as a new user and using the DAC on a RET6

   So far I love everything about this community.
   You guys do all the right stuff, the best way and aren't even snobby about it.
   I think the hardware is very slick (but, of course, I want more).

   I've had no problems installing software, finding or understanding documentation (Windows XP SP3).

   The only annoyance (as warned in the documentation) is some flakiness during Upload from the IDE under Windows. The process hangs just before it starts making Xs to show upload progress. I can always fix the condition by putting the Maple in permanent upload mode (reset and hit "BUT" like the installation instructions) and hitting Upload again. It hangs some 15% of Upload attempts.

   The DAC on the RET6 has two channels: 1 and 2
   Channel 1 is on Pin 10 and channel 2 is on Pin 13 of the Maple.
   As mentioned in the Maple RET6 Edition, dac channel 2, Pin 13 is also "The LED".
   Besides the pin numbers, everything you need to know is in one wiki page (search "dac").
   I just copy/pasted the code from the wiki and was up and running.
   I haven't tried anything fancier than just writing to the dac but that seems to work fine and puts the dac in buffered mode like its supposed to.
   I only tried channel 1.
   It also appears that you can analog read the dac pin. I haven't verified this in the hardware documentation so it could be a "ghost" connection. I'm going to run it down as this could be handy for Sigma calculations.

   I'm, just now, contemplating the ramifications of removing "The LED" to better expose my other dac channel. Anyone have any thoughts on this.

   Posted 3 years ago #
2. 

   gbulmer
   Moderator

   If you get the High density STM32F103 data sheet:
   http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00191185.pdf

   You can see that the DAC's are on pin PA4 and PA5 (Port A, bit 4, and 5), which are pin 20 and pin 21.
   In "Table 5. High-density STM32F103xx pin definitions", you can see the other functions on those pins:
   LQFP64 20, PA4: SPI1_NSS USART2_CK DAC_OUT1 ADC12_IN4
   LQFP64 21, PA5: SPI1_SCK DAC_OUT2 ADC12_IN5

   So, yes, those can be sampled by either ADC 1 or ADC 2. LeafLabs libmaple library only uses ADC1.

   Yes, the LED being on the DAC2 pin is sad. IIRC, the RET6 board is the same PCB as a Rev5 Maple, so there were no changes to give better access to the extra MCU resources.

   The main problem (I can think of) with using DAC2 is some of the LeafLabs code relies on using the LED on pin13 to signal events. So if you do connect something to the DAC output, without changing any code, there is a risk of having that pin driven as a digital output.

   AFAIK, all of that is controlled by a #define in the bootloader, and the 'pin map' which is different for each board.
   So you change the 'pin 13' #define in the bootloader, and fix the library with a new pin map, and that should solve those problems (search this forum for more detail).

   It might be worth asking LeafLabs, or anyone else, if they have a version of code which does that already.

   (Full disclosure: I am not a member of LeafLabs or Olimex staff)

   Posted 3 years ago #

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